1. Field of the Invention
The present invention relates to a method of removing a dismountable toroidal support from a cured tyre, of the type comprising the steps of: positioning a toroidal support carrying a cured tyre in a dismantling station, said toroidal support comprising a plurality of sectors circumferentially distributed around a geometric reference axis and fastened to each other by a flange and a counter-flange mutually in engagement at axially opposite positions with respect to the sectors; disengaging the counter-flange from the flange; axially moving the flange and counter-flange away from the sectors; removing each sector from the tyre by a centripetal radial translation movement.
2. Description of the Related Arts
Production of a tyre for vehicle wheels essentially involves a manufacturing step in which the different constructional elements of the tyre are assembled following a preestablished sequence, and a subsequent vulcanization step in which, through pressing within a mould and simultaneous administration of heat, molecular cross-linking of the elastomer material employed in forming said constructional elements is caused, which will, as a result, bring about structural and dimensional stabilization of the tyre itself.
It should be pointed out, for the purposes of the present description, that by the term xe2x80x9celastomer materialxe2x80x9d it is intended the rubber blend in its entirety, i.e. the assembly formed of at least one base polymer suitably amalgamated with reinforcing fillers and process additives of various types.
The traditional production methods essentially involve that the constructional elements of the tyre, such as carcass plies, anchoring annular structures for the tyre beads, belt structure, sidewalls, tread band, etc. should be first made separately from each other, to be then sequentially assembled during the tyre manufacturing process.
The Applicant""s present trend is however that of resorting to manufacturing methodologies enabling production and storage of semifinished products to be minimized or, possibly, eliminated.
Practically, research and development are presently addressed to new process solutions enabling the individual components to be made by directly forming them on the tyre being manufactured according to a preestablished sequence.
In this connection, manufacturing processes have been recently proposed and developed, by the Applicant itself as well, in which assembling of the components during the tyre manufacture takes place on a rigid toroidal support which is then introduced into a vulcanization press together with the tyre to be cured. When vulcanization has been completed, the rigid toroidal support must be removed from the tyre previously extracted from the vulcanizing unit.
To enable this removal, use of collapsible or dismountable toroidal supports is usually provided, which supports are made up of a plurality of circumferential sectors lending themselves to be individually retracted in a radial direction towards the rotation axis of the tyre for disengagement from the tyre itself passing through the space defined between the tyre beads.
Such a dismountable toroidal support is described in U.S. Pat. No. 4,106,888 for example, where provision is made for the presence of a first and a second series of circumferential sectors disposed in alternated relationship with each other and connected to respective linkages that, during a first step, carry out a radial translation inwardly of the tyre of the sectors belonging to the first series and axially extract said sectors from the tyre itself, in order to free the required space for radial translation of the sectors belonging to the second series which is accomplished during a subsequent step.
To avoid too many stresses being imposed to the tyre during radial translation of the sectors, appropriate grip members cause the tyre beads to be mutually open wide in an axial direction to enable extraction of the sectors in the absence of interference.
In document U.S. Pat. No. 4,116,596, in order to limit stresses on the tyre, the individual sectors are provided to have a structure which can contract in a radial direction, so that said sectors can pass between the tyre beads without the latter being required to open too wide.
Document EP 893 237 discloses a dismountable toroidal support in which mutual connection between the circumferential sectors is ensured by two axially opposite annular flanges that are kept in axial thrust relationship on opposite sides of the toroidal support by a cylindrical sleeve axially extending through the toroidal support itself. One end of the cylindrical sleeve acts against one of the flanges by means of a circumferential abutment, whereas the opposite end gets operatively in engagement with the other flange by screwing or bayonet coupling.
Removal of the toroidal support from the cured tyre involves that, at a dismantling station in which engagement of the tyre has been previously carried out, the cylindrical sleeve together with one of the flanges should be disengaged from the counter-flange and associated with a counter-flange and respective circumferential sectors previously arranged in an adjacent assembling station in order to constitute a new toroidal support which will be subsequently moved away. The tyre, together with the circumferential sectors of the toroidal support, is temporarily removed from the dismantling station to enable transfer of the counter-flange to the assembling station. When transferring is over, the tyre is engaged again in the dismantling station to enable removal of the circumferential sectors. Each sector is extracted from the tyre by a centripetal radial movement, to be subsequently transferred onto a respective support element arranged in the assembling station. When all sectors have been transferred to the assembling station, a radial movement of the respective support elements causes the same to circumferentially move close to each other, so that they are ready to engage a new sleeve with the respective flange, which have been removed from the toroidal support associated with the subsequent tyre transferred to the dismantling station.
In accordance with the present invention, it has been found that by imposing to the sector which is about to be extracted from the tyre, a rotation motion within the tyre itself, the risks of imposing anomalous stresses to the tyre can be drastically reduced, which will enable the sectors to be extracted even when the tyre is still hot, immediately after its extraction from the vulcanizing unit.
In particular, it is an object of the present invention a method of removing a dismountable toroidal support from a cured tyre, characterized in that to at least one of said sectors, concurrently with said centripetal radial translation movement, an angular rotation movement is transmitted which takes place around an axis substantially normal to a direction radial to said geometric reference axis and lying in a meridian plane axially offset with respect to an equatorial plane of the tyre.
In more detail, said angular rotation movement is preferably carried out in two opposite directions in at least one first and one second consecutive steps of angular oscillation of the sector around a first and a second oscillation axes located on opposite sides with respect to the equatorial plane.
It is also preferably provided that the angular rotation movement should be at least partly carried out before the centripetal radial translation movement begins.
Advantageously, during removal of each sector from the tyre, the step of rigidly retaining the other sectors still engaged in the tyre is carried out.
In a preferential embodiment, the toroidal support comprises a first series of sectors circumferentially delimited by end sides that do not diverge radially away from said geometric reference axis, and a second series of sectors, which are each interposed between two sectors belonging to said first series, said angular rotation movement being transmitted at least to the sectors belonging to the first series.
Preferably, removal of the sectors belonging to the second series is carried out upon removal of all sectors belonging to the first series.
According to a further aspect of the present invention, also provided is the step of creating a fluid flow between the inner surface of the tyre and the outer surface of the toroidal support before removal of each sector from the tyre.
In more detail, a fluid flow is created simultaneously with opening of a mould in which a vulcanization step has been previously carried out on the tyre.
Preferably, also carried out are the steps of: transferring each sector, concurrently with said removal step, to a reassembling station in which an auxiliary counter-flange previously picked up from a toroidal support dismounted in a previous work cycle has been arranged; transferring said flange to the reassembling station after transfer of all sectors has been completed; engaging said flange with the auxiliary counter-flange to put a toroidal support together again in the reassembling station; removing the toroidal support put together from the reassembling station; transferring said counter-flange to the reassembling station to use it in reassembling a dismounted drum in a subsequent work cycle.